1. Field of the Invention
The present invention relates to a drive mode estimating device for a motor vehicle, which is adapted to estimate a vehicle drive mode desired by the vehicle operator, and an apparatus which uses an output of such a drive mode estimating device, for controlling a controllable system of a vehicle, such as a shift control apparatus for controlling an automatic transmission and a drive force control apparatus for controlling a drive force of the vehicle.
2. Discussion of the Related Art
A motor vehicle may be equipped with various control devices, which include: a shift control device for controlling an automatic transmission having a plurality of speed ratios or gear positions, so as to automatically shift the transmission to an appropriate gear position, on the basis of currently detected engine load and vehicle running speed and according to predetermined shift patterns; a steering control device for controlling the steering force of a power steering system; a suspension control device for controlling the damping force or spring characteristics of a shock absorber in the suspension system; and a throttle valve control device for controlling a throttle valve on the basis of a currently detected amount of operation of an accelerator pedal and according to a predetermined relationship between the throttle valve opening angle and the amount of operation of the accelerator pedal. Generally, it is desirable to control these control devices so that the vehicle drive mode desired by the vehicle operator is reflected on the controlled vehicle drive torque, steering force of the steering system, damping force or spring characteristics of the shock absorber, and throttle opening angle.
There have been proposed some techniques for reflecting the vehicle operator's desired drive mode on the manner of control of an automatic transmission. An example of such techniques is disclosed in JP-A-6-221420, wherein a suitable one of different shift patterns for the automatic transmission is selected depending upon whether the vehicle operator desires to drive the vehicle in a sporty drive mode with a comparatively high degree of drivability, or in an economy drive mode with a relatively high degree of fuel economy. A determination as to whether the vehicle operator desires the sporty drive mode or the economy drive mode is based on output signals of various sensors provided on the vehicle, which signals are processed by a neural network which utilizes previously obtained data indicative of relationships between the vehicle drive modes and drive mode indicating parameters or variables detected by the sensors.
For instance, one of the different shift patterns is selected on the basis of the rate of change of the opening angle of a throttle valve of an engine, when the throttle opening angle is larger than a predetermined threshold. An example of a shift control apparatus adapted to practice this technique is disclosed in JP-B-58-31499.
The conventional shift control methods for the automatic transmission, as disclosed in JP-A-6-221420, uses a neural network which is adapted to receive signals indicative of vehicle running speed, opening angle of a throttle valve, vehicle acceleration, activation of a braking system, a currently selected gear position of the transmission, and a rate of change of the throttle valve opening. The vehicle drive mode desired by the vehicle operator is estimated on the basis of a relatively large number of outputs of the neural network which are considered to represent the operator's desired vehicle drive mode. This arrangement does not permit sufficiently high accuracy of estimation of the desired vehicle drive mode in a short time. If the number of the outputs of the neural network used to estimate the desired vehicle drive mode is increased to improve the reliability of estimation of the desired drive mode, the operating response of the neural network to the operator's manipulation to drive the vehicle is inevitably deteriorated, whereby the actual control of the vehicle does not meet the operator's desired drive mode.
In the shift control apparatus disclosed in JP-B-58-31499, one of the shift patterns is selected depending upon the rate of change of the opening angle of the throttle valve, even if the opening angle of the throttle valve is abruptly changed (abruptly increased and decreased) in a short time, as long as the throttle opening angle is larger than the threshold. The abrupt change of the throttle opening angle does not necessarily reflect the drive mode of the vehicle desired by the vehicle operator, and the transmission shift pattern selected on the basis of the abrupt change of the throttle opening angle does not necessarily meet the operator's desired drive mode of the vehicle. Thus, this conventional technique does not permit sufficiently accurate estimation of the operator's desired drive mode.
JP-A-3-204468 discloses a technique for determining a control pattern for a continuously variable transmission of a motor vehicle, on the basis of a rate of change of a drive mode index value which reflects a vehicle operator's intention regarding the vehicle drive mode, and an average value of the rate of change. This publication JP-A-3-204468 also discloses a technique for fuzzy inference of such a drive mode index value, on the basis of a difference between a maximum value of an increase rate of the opening angle of a throttle valve and an average value of the increase rate, and the opening angle of the throttle valve. JP-A-7-167272 discloses a technique for estimating a drive mode index indicative of the degree of the vehicle operator's desire to accelerate the vehicle, with improved estimation response, wherein a higher one of the engine load and the tire load is obtained, and this higher load value is filtered with a filtering constant which is changed depending upon the rate of change of the amount of operation of the accelerator pedal and a change in the load value.
In the above techniques, however, a tendency of change of the presently detected drive mode indicating variables from the drive mode indicating variables detected in the past is not taken into account to obtain the drive mode index, and therefore the obtained drive mode index does not accurately represent the vehicle operator's desired drive mode which meets the operator's manipulation of the vehicle and the running conditions such as the road condition. These conventional techniques which do not utilize the past drive mode indicating variables may suffer from erroneous estimation of the operator's desired drive mode, since a change in the operator's desired drive mode may not be reflected by the operator's manipulation of the vehicle under some operating and running conditions of the vehicle. The use of the filtering constant which varies with the variables detected for a relatively short time period is not effective enough to prevent the erroneous estimation of the operator's desired vehicle drive mode.